The design, evaluation and optimization of complex aerodynamic geometries involves extensive wind-tunnel testing and/or computationally-intensive numerical simulations. Even in the latter case, high-quality experimental wind-tunnel work with minimal, quantifiable errors is still necessary for code-validation purposes. Moreover, in aerodynamic testing facilities where large volumes of data need to be acquired in tight schedules, "down" time due to instrumentation lack of performance is highly undesirable. Such facilities include, among others, industrial testing wind tunnels, as well as high-productivity CFD code validation facilities.
In such environments, flow measurement techniques such as Laser-Doppler Velocimetry (LDV) and Particle Image Velocimetry (PIV), although powerful, usually require painstaking efforts for their successful usage. Costly components, complex setups, troublesome flow "seeding" requirements, lack of flexibility, ruggedness and mobility and ease of misalignment often render such techniques impractical. Moreover, in testing of complex three-dimensional geometries, accessibility of the entire flow-field around the model is an essential issue. When employing optical techniques, large sections of the flow-field are physically obstructed by the presence of the model. To access such regions, repositioning of the instrumentation setup may be necessary. This is a time-consuming process having associated potential pitfalls.
Multi-hole pressure probes have in many cases provided the easiest-to-use and most cost-effective method for three-component flow velocity measurements in research and industry environments. However, even though the measurement capabilities of such instruments have been expanded, the current pressure probe configurations and techniques have only a limited range of velocity inclinations that they can measure. Conventional probes are limited to five- or seven-hole configurations with conical probe heads. Current probes and techniques also have severe frequency-response limitations.